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Diversity and dispersal of the ophiostomatoid fungus, Knoxdaviesia proteae, within Protea repens infructescences

Aylward, Janneke (2014-04)

Thesis (MSc)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Two genera of ophiostomatoid fungi occur in the seed-bearing structures of serotinous
Protea species in the Cape Floristic Region. These fungi are dispersed by arthropods,
including mites and beetles that visit the Protea host plants. Although the vectors of Proteaassociated
ophiostomatoid fungi are known, their dispersal patterns remain unknown –
especially the manner in which recently burnt fynbos vegetation is recolonized. Additionally,
their reproduction strategy has not previously been investigated. The focus of this study was,
therefore, to determine the extent of within- and between-plant dispersal of Proteaassociated
ophiostomatoid fungi at the population level and to investigate their reproductive
strategy. One Protea-associated ophiostomatoid fungus, Knoxdaviesia proteae, is found
exclusively in the fruiting structures of P. repens and was the focus of this study. In order to
interrogate natural populations of this fungus, 12 polymorphic microsatellite markers
specific to K. proteae were developed with an ISSR-PCR enrichment strategy and
pyrosequencing. These markers were amplified in two distantly separated populations of K.
proteae. The genetic and genotypic diversities of both populations were exceptionally high
and neither showed significant population differentiation. The lack of population structure in
both populations implies that K. proteae individuals within a P. repens stand are in
panmixia. As one of the sampling sites had burnt recently, the process whereby young
fynbos is recolonized could be investigated. Compared to the adjacent, unburnt area, K.
proteae individuals in the burnt area of this population had significantly less private alleles,
suggestive of a young population that had experienced a genetic bottleneck. Knoxdaviesia
proteae individuals that did not originate from the adjacent unburnt area were encountered
within the burnt site and, additionally, isolation-by-distance could not be detected. The
parsimony-based haplotype networks and the tests for linkage disequilibrium indicated that
recombination is taking place within as well as between the two distantly separated
populations. The observed panmixia in P. repens stands, widespread recolonization and the high genetic similarity and number of migrants between the two populations emphasizes
long-distance dispersal and therefore the role of beetles in the movement of K. proteae. This
cohesive genetic structure and connection across large distances is likely a result of multiple
migration events facilitated by beetles carrying numerous phoretic mites.